Part Number: TMS320F28388D
Other Parts Discussed in Thread: AMC3301
Hi experts,
We develop our original board with F28388D.
We debug and evaluate it on ADC function(16-bit, differential mode) with below equipment.
AdecaRegs.ADCCTL2.bit.PRESCALE = 0. (ADC clock = System Clock = 200MHz)
Sampling & Hold time is 1000ns (for a debug)
When the voltage source outputs from 0mV to 8mV, ADC result (ADCA2,3, 16-bit, differential) is a constant (0x82d1) value in a AdcdA adc result register.
And only when the voltage source outputs 0mV, 0x72df as ADC result is often detected like a spike noise in the adc result register.
And when the voltage source outputs more than 8mV, ADC result is not constant (we expect).
Could you please comment about this behavior ? Is it a ADC correct specification ?
What registers we should check ?
We suspect that this behavior (we do not expect) would be related a common mode voltage.
In a datasheet of AMC3301, common mode output voltage is 1.44V(Typical), 1.39 - 1.49V.
However F28388D requires that ADC input signal common mode voltage is from (VREFCM - 50mv) to (VREFCM - 50mv)
In our board, VREFHI is 3.0V and VREFCM will be 1.50V.
Best regards,
Hidehiko
